A. Technical Field
The present invention relates to micro-electro-mechanical-system (MEMS) gyroscopes. More particularly the invention relates to MEMS systems, devices, and methods to operate multi-axial MEMS gyroscopes and provide immunity against environmental mechanical disturbances.
B. Background of the Invention
In recent years, the market for MEMS gyroscopes has seen rapid increases in the demand for MEMS gyroscopes designed for applications such as consumer electronics and automotive. As a result, two distinctive trends have crystallized in the development of modern gyroscopes.
First, the trend to miniaturization of gyroscopes has led to designs that integrate multiple MEMS sensors into a single device that is capable of simultaneously sensing angular velocity around multiple spatial axes. An example of multi-axial integration of gyroscopic sensors for low-end devices, where small size is a key design parameter, is presented in U.S. patent application serial number 2011/0094301. Second, immunity to environmental disturbances such as vibrations, shock and other sudden impact of forces has become a key requirement in the high-end gyroscopic device market. An example of a shock-robust gyroscope that is designed to counteract environmental disturbances by electrical and mechanical means is presented in U.S. patent application serial number 2013/0269469.
At a glance, it appears that integrating multi-axial sensors into high-end gyroscopic devices would allow for more sophisticated and demanding applications in the consumer market as well as reduce cost for automotive applications. However, high-end shock-robust gyroscopes are inherently complex devices that incorporate redundant differential structures. A direct integration of a three single-axis high-end gyroscope on the same silicon substrate poses complex challenges that have not been mastered to date. In addition, the increase in complexity of designing a suitable control system has kept the above-mentioned two trends practically distinct thus far.
While some efforts are being undertaken to design stabilization and shock robustness features into MEMS gyroscopes that, for example, could prevent accidents and potentially save lives in safety-related applications, the automotive field continues to rely on independent single-axis high-end gyroscopes integrated at board level. Ideally, these gyroscopes would always remain operative even in scenarios in which disturbing forces from shock events are transmitted to the appropriate sensing circuit of the MEMS gyroscope so as to maintain directional stability by distinguishing between the different contributions of forces that cause displacement of proof masses, detecting unwanted spinning, etc., and taking appropriate corrective action in various shock scenarios.
What is needed are designs that successfully combine the advantages of the two above-mentioned trends to create reliable, shock-robust, multi-axis gyroscopic sensors.